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Advanced Communications Technology Satellite (ACTS)

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Earth Stations


An Illustration depicting the various interactions between ACTS and earth stations. The ACTS network comprised a variety of terminal types. Two general categories of terminals were developed: fixed and mobile earth stations. Some of the terminals were developed at Glenn Research Center. Outside investigators also developed their own terminals. Terminals were designed to operate in either BBP mode or MSM mode.

The two types of earth stations used in control of and experiments with ACTS are the Master Ground Station (MGS) and Satellite Operations Center (SOC); and Experimental Terminals.

The Master Ground Station (MGS) and the Satellite Operations Center (SOC)

Master Ground Station and Satellite Operations Center at NASA Glenn Research CenterThe ground control segment of ACTS includes the Master Ground Station (MGS) located at NASA Glenn Research Center in Cleveland, Ohio; and the Satellite Operations Center (SOC) located at Lockheed Martin's Commercial Space Systems facility in Newtown, Pennsylvania. Basically, the MGS controls the experimental equipment onboard the spacecraft, while the SOC controls the maneuvering of the spacecraft.

The Master Ground Station provides spacecraft and network control, manages experiments and user investigations, and records spacecraft and system data. Traffic requests are processed and set up and traffic channels are assigned on an on-demand basis. Command, ranging and telemetry information is sent to and from ACTS via the MGS. All communications, including commanding and telemetry, to the spacecraft are done through this facility. A 5.5m tracking antenna is used. The command link has approximately 25dB of link margin.

The Satellite Operations Center provides 24 hour monitoring of the spacecraft health and status. Its primary responsibility is generating flight system commands and analyzing, processing and displaying the data from the flight system's instruments. The center also handles orbital maneuvering as well as housekeeping functions. The SOC is linked by terrestrial line to equipment in the Master Ground Station.

Collage of earth terminalsExperimenter Terminals

In addition to the satellite, a network of earth terminals was developed by NASA to serve certain classes of user application experiments as well as some unique terminals developed by experimenters. The user terminals consisted of a variety of earth terminals operated by industry, university and government entities located across the United States. More than one hundred investigators, using over 53 earth stations participated in the ACTS program.

The primary experimenter terminals developed by NASA included: